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Author: Florent Baboux
Publisher:
ISBN:
Category :
Languages : fr
Pages : 204
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Book Description
Cette thèse est consacrée à l'étude des effets du couplage spin-orbite dans des puits quantiques semi-conducteurs dopés (GaAs et CdMnTe), par spectroscopie Raman électronique. Dans ces structures existent des champs magnétiques intrinsèques (Dresselhaus et Rashba). Ces champs offrent des moyens attractifs pour manipuler le spin des électrons, mais contribuent aussi à la relaxation de spin via leur dépendance avec le vecteur d'onde de l'électron (mécanisme D'yakonov-Perel'). Nous montrons que pour les modes collectifs de spin de puits quantiques, le scénario destructif D'yakonov-Perel' est transformé en un scénario constructif : les interactions Coulombiennes font émerger un champ spin-orbite collectif, proportionnel au vecteur d'onde de l'excitation, et renforcé d'un facteur de plusieurs unités par rapport aux champs spin-orbite individuels. Nous mettons d'abord en évidence ces effets spin-orbite géants sur le plasmon de spin inter-sous-bande, dans des puits quantiques de GaAs. Le champ spin-orbite collectif, qui conduit à un éclatement de structure fine du spectre plasmon, est superposé à un champ magnétique extérieur et cartographié dans l'espace réciproque. Nous étudions ensuite l'onde de spin intra-sous-bande du gaz d'électrons polarisé en spin, dans des puits quantiques magnétiques dilués de CdMnTe. Le champ spin-orbite collectif se superpose ici au champ Zeeman géant du composé. Nous mesurons le facteur de renforcement du champ spin-orbite collectif. Enfin, nous démontrons la possibilité de contrôler l'amplitude du champ spin-orbite collectif à l'aide d'une grille optique et nous mesurons la dépendance du facteur de renforcement avec la densité électronique.
Author: Florent Baboux
Publisher:
ISBN:
Category :
Languages : fr
Pages : 204
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Book Description
Cette thèse est consacrée à l'étude des effets du couplage spin-orbite dans des puits quantiques semi-conducteurs dopés (GaAs et CdMnTe), par spectroscopie Raman électronique. Dans ces structures existent des champs magnétiques intrinsèques (Dresselhaus et Rashba). Ces champs offrent des moyens attractifs pour manipuler le spin des électrons, mais contribuent aussi à la relaxation de spin via leur dépendance avec le vecteur d'onde de l'électron (mécanisme D'yakonov-Perel'). Nous montrons que pour les modes collectifs de spin de puits quantiques, le scénario destructif D'yakonov-Perel' est transformé en un scénario constructif : les interactions Coulombiennes font émerger un champ spin-orbite collectif, proportionnel au vecteur d'onde de l'excitation, et renforcé d'un facteur de plusieurs unités par rapport aux champs spin-orbite individuels. Nous mettons d'abord en évidence ces effets spin-orbite géants sur le plasmon de spin inter-sous-bande, dans des puits quantiques de GaAs. Le champ spin-orbite collectif, qui conduit à un éclatement de structure fine du spectre plasmon, est superposé à un champ magnétique extérieur et cartographié dans l'espace réciproque. Nous étudions ensuite l'onde de spin intra-sous-bande du gaz d'électrons polarisé en spin, dans des puits quantiques magnétiques dilués de CdMnTe. Le champ spin-orbite collectif se superpose ici au champ Zeeman géant du composé. Nous mesurons le facteur de renforcement du champ spin-orbite collectif. Enfin, nous démontrons la possibilité de contrôler l'amplitude du champ spin-orbite collectif à l'aide d'une grille optique et nous mesurons la dépendance du facteur de renforcement avec la densité électronique.
Author: Francisco José Teran Garcinuno
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
L'étude des propriétés électroniques et magnétiques des structures à un puits quantique CdMnTe à modulation de dopage de type-n nous a permis d'explorer l'interaction d'échange sp-d entre les électrons 2D délocalisés et les moments magnétiques localisés des ions Mn2+. Cette interaction d'échange sépare les états de spin éléctronique induisant un splitting Zeeman géant lequel modifie profondément les propriétés électroniques et optiques du semi-conducteur. A faible champ magnétique, l'interaction sp-d peut être décrite par une approximation de champ moyen. Néanmoins, à fort champ magnétique nous observons qu'une énergie effective Zeeman nulle n'entraîne pas la disparition complète du gap de spin. En effet, des expériences de transport et de spectroscopie Raman montrent une répulsion entre les niveaux se spin up et down. Nos résultats peuvent être expliqués dans le cadre d'un modèle basé sur l'anti-croisement des niveaux de Landau résolus en spin. Les propriétés magnétiques du sous-système d'ions Mn2+ snt fortement influencées par la présence des porteurs. Le 'knight shift' observé pour la position du spectre RPE peut être décrit par l'approximation de champ moyen pour de faibles champs. Cependant, cette approximation ne permet pas de décrire la valeur importante du 'knight shift' à fort champ au voisinage de EMnz=Eez. Pour interpréter nos résultats expérimentaux de spectroscopie Raman et de Rpe nous proposons un modèle basé sur l'interaction résonante entre les excitations de spin pour les électrons et pour les ions Mn2+. Finalement, une étude de l'évolution de la réponse optique des puits quantiques CdMnTe en fonction de la concentration d'électrons montre une persistance des effets excitoniques lorsque l'énergie de Fermi est comparable à l'énergie de liaison excitonique. Suite à nos recherches, l'homogénéité de nos systèmes est remise en cause.
Author: Jacques Lafontaine
Publisher: Springer
ISBN: 3319207350
Category : Mathematics
Languages : en
Pages : 408
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Book Description
This book is an introduction to differential manifolds. It gives solid preliminaries for more advanced topics: Riemannian manifolds, differential topology, Lie theory. It presupposes little background: the reader is only expected to master basic differential calculus, and a little point-set topology. The book covers the main topics of differential geometry: manifolds, tangent space, vector fields, differential forms, Lie groups, and a few more sophisticated topics such as de Rham cohomology, degree theory and the Gauss-Bonnet theorem for surfaces. Its ambition is to give solid foundations. In particular, the introduction of “abstract” notions such as manifolds or differential forms is motivated via questions and examples from mathematics or theoretical physics. More than 150 exercises, some of them easy and classical, some others more sophisticated, will help the beginner as well as the more expert reader. Solutions are provided for most of them. The book should be of interest to various readers: undergraduate and graduate students for a first contact to differential manifolds, mathematicians from other fields and physicists who wish to acquire some feeling about this beautiful theory. The original French text Introduction aux variétés différentielles has been a best-seller in its category in France for many years. Jacques Lafontaine was successively assistant Professor at Paris Diderot University and Professor at the University of Montpellier, where he is presently emeritus. His main research interests are Riemannian and pseudo-Riemannian geometry, including some aspects of mathematical relativity. Besides his personal research articles, he was involved in several textbooks and research monographs.
Author: P. M. Banks
Publisher: Elsevier
ISBN: 1483260666
Category : Science
Languages : en
Pages : 445
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Book Description
Aeronomy, Part A is an attempt to make a comprehensive exposition of the processes in aeronomy, the study of composition, movement, and thermal balance of the upper regions of the planetary atmosphere. The text covers topics such as atmospheric regions and atmospheric density, the temperature and molecular mass of the atmosphere; the permanent constituents and the molecular and isotonic composition of the homosphere; and the transition from the homosphere to the heterosphere. Also covered are topics such as the temperature gradient and energies in the thermosphere, conditions at 200km and above 250km, solar radiation and ionization, and aeronomic reactions. The book is recommended for scientists, especially natural physicists, who would like to know more about the field of aeronomy and its advances.
Author: Sue Blattes
Publisher: L'Editeur : EDP Sciences
ISBN: 9782868835888
Category : English language
Languages : fr
Pages : 264
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Book Description
Cet ouvrage, devenu célèbre sous son sigle MCSE, a déjà été utilisé par plus de 50 000 étudiants, chercheurs, professionnels. L'objectif est de lire et écrire des textes en anglais scientifique avec facilité et pertinence. L'ouvrage est conçu pour que l'apprenant devienne un véritable utilisateur de l'anglais. La méthode originale repose sur l'analyse des fonctions et structures nécessaires : measurement, frequency, comparison, modification, link words, time, cause and consequence, hypothesis, modality, purpose and process, impersonal forms, compound nouns and adjectives. Dans chaque unit, des tests d'auto-évaluation permettent de se situer et de construire son parcours de formation, d'abord en définissant ses objectifs à l'aide des key points et du lexis, puis, de façon plus personnalisée, en puisant dans les examples in context, checkpoints (back to basics, word web), web search, FAQs... MCSE est l'outil de base d'une méthode qui comprend aussi d'autres outils dans la même collection (Listening Comprehension for Scientiflc English et Speaking Skills in Scientitic English). L'ouvrage est destiné à tout apprenant de niveau baccalauréat qui désire acquérir une réelle compétence dans l'écriture et la lecture de textes en anglais scientifique.
Author: Camille Flammarion
Publisher:
ISBN:
Category : Astronomy
Languages : en
Pages : 732
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Book Description
Author: Barton C. Hacker
Publisher: JHU Press
ISBN: 0801887720
Category : History
Languages : en
Pages : 230
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Book Description
The growth of American engineering and science has affected military technology, organization, and practice from the colonial era to the present day—even as military concerns have influenced, and often funded, domestic engineering programs and scientific development. American Military Technology traces the interplay of technology and science with the armed forces of the United States in terms of what Hacker and Vining view as epochs: 1840–1865, the introduction of modern small arms, steam power, and technology, science, and medicine; 1900–1914, the naval arms race, torpedoes and submarines, and the signal corps and the airplane; and 1965–1971, McNamara's Pentagon, technology in Vietnam, guided missiles, and smart bombs. The book is an excellent springboard for understanding the complex relationship of science, technology, and war in American history.
Author: I. B. Holley, Jr.
Publisher: Createspace Independent Pub
ISBN: 9781478344865
Category : History
Languages : en
Pages : 174
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Book Description
The author's interest in Air Force doctrine was first aroused when he was a sergeant serving as an aerial gunnery instructor in early 1943. When the operational research people revealed that what we were teaching was faulty, he came to realize that the Air Force system for developing doctrine was flawed. The problem continued to interest him and later, after he was commissioned and serving on the faculty of the Industrial College of the Armed Forces, he wrote his book Ideas and Weapons using the experience of the air arm to expound the need for a more systematic procedure for developing doctrine. Because the doctrinal materials gathered on World War II were still highly classified, he reverted to World War I to put across his thesis without violating security. The author's real concern was to contribute to the soon to be established US Air Force in the search for a more effective means of formulating doctrine. The essays that follow reflect how his ideas developed over the 30-odd years of my Air Force career. Inevitably there are some overlaps and repetitions given the origin of these essays as articles and lectures spread over many years. The main themes are evident. He repeatedly made the case for the importance of doctrine and the need to perfect the technological advances in equipment. He was concerned to see that doctrine was continually perfected in peacetime and not just in wartime when the pressure of enemy performance provides a powerful incentive to do this. Another theme repeatedly stated was the need for officers suitably educated to see the importance of doctrine and realize that doctrine is literally “everybody's business” and not just the concern of a handful of individuals assigned to the formal task of compiling doctrinal manuals. These people are important, but they cannot perform effectively if officers throughout the service fail to write after-action reports summarizing their valuable experiences, not just in air operations but in all aspects of the air arm activities, procurement, personnel administration, logistics, and legislative liaison. One can easily make the case that improving the ability of the Air Force to cope with Congress is just as important as suggesting the best possible doctrine for aerial combat. One can't just assume that every newly promoted flag officer will instinctively understand the best way of testifying on Capitol Hill. Much of the doctrinal problem within the Air Force stems from the professional education of officers. Unless they are rigorously educated to undertake the objective analysis of recorded historical experience, all the most carefully edited doctrinal manuals will avail little. One of the author's insistent themes is the need to make doctrinal manuals not only more readable but more memorable. To this end several of the following essays are addressed to those who are assigned as doctrinal writers.
Author: Catherine Barnard
Publisher: Bloomsbury Publishing
ISBN: 184731869X
Category : Law
Languages : en
Pages : 337
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Book Description
The Cambridge Yearbook of European Legal Studies provides a forum for the scrutiny of significant issues in EU Law, the law of the European Convention on Human Rights, and Comparative Law with a 'European' dimension, and particularly those issues which have come to the fore during the year preceding publication. The contributions appearing in the collection are commissioned by the Centre for European Legal Studies (CELS) Cambridge, a research centre in the Law Faculty of the University of Cambridge specialising in European legal issues. The papers presented are at the cutting edge of the fields which they address, and reflect the views of recognised experts drawn from the University world, legal practice, and the institutions of both the EU and its Member States. Inclusion of the comparative dimension brings a fresh perspective to the study of European law, and highlights the effects of globalisation of the law more generally, and the resulting cross fertilisation of norms and ideas that has occurred among previously sovereign and separate legal orders. The Cambridge Yearbook of European Legal Studies is an invaluable resource for those wishing to keep pace with legal developments in the fast moving world of European integration. INDIVIDUAL CHAPTERS Please click on the link below to purchase individual chapters from Volume 13 through Ingenta Connect: www.ingentaconnect.com SUBSCRIPTION TO SERIES To place an annual online subscription or a print standing order through Hart Publishing please click on the link below. Please note that any customers who have a standing order for the printed volumes will now be entitled to free online access. www.hartjournals.co.uk/cyels/subs Editorial Advisory Board: Albertina Albors-Llorens, John Bell, Alan Dashwood, Simon Deakin, David Feldman, Richard Fentiman, Angus Johnston, John Spencer Founding Editors: Alan Dashwood and Angela Ward Ius Commune Prize 2012 Alexandre Saydé wrote Chapter 15 in this volume entitled: 'One Law, Two Competitions: An Enquiry into the Contradictions of Free Movement Law' and we are delighted to announce that he has been awarded the Ius Commune Prize 2012.
Author: Philip K. Dick
Publisher: Read Books Ltd
ISBN: 1473379385
Category : Fiction
Languages : en
Pages : 18
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Book Description
From the visionary mind of Philip K. Dick, author of sci-fi classics that inspired blockbusters like Blade Runner, Total Recall, and Minority Report, comes Beyond Lies the Wub, a masterful exploration of paranoia, suspense, and mind-bending cosmic revelations. Peterson, a crew member on a spaceship resupplying on Mars, encounters the intriguing wub, an enormous pig-like creature with hidden depths. As they venture off the Martian landscape, the crew realizes that the wub is far more intelligent than they could have ever imagined, possessing telepathic powers and even the potential for mind control. Embark on a journey like no other as conversations unfold between Peterson and the wub about mythology, the epic travels of Odysseus, and the very boundaries of consciousness. Tensions rise as Captain Franco, tormented by paranoia, develops a fearful obsession with the wub; putting the entire crew's safety, loyalties, and understanding of reality at risk. In the tradition of pulp fiction and speculative fiction titans, Dick weaves a suspenseful tale that will keep sci-fi enthusiasts on the edge of their seats. Unearth the true power of the enigmatic wub in this captivating cosmic adventure that explores the thin line between humanity's compassion and destructive tendencies.
